158 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
host and develop normally in its tissues, thus many skates, 
rays and dogfishes eat other food animals which contain 
Tetrarhynchus larvae and the latter undergo transformation 
and develop into adult tapeworms in the intestine of the fish 
which is their final host. (2) The same infected food animals 
may be eaten by a halibut, gurnard or some other fishes which 
cannot serveasthefinalhosts. Insucha case the Tetrarhynchus 
larvae become encysted and finally die without undergoing 
development. That seems to be what has occurred in the 
tripe-infection now recorded: the organisms (Cestodes or 
Sporozoan parasites) that acted as the nuclei of the pearl-like 
bodies did not find their true, final host and so became encysted 
and destroyed with the results described here. 
